Acoustic lamina wall covering

ABSTRACT

A moisture-permeable acoustic lamina which is usable as a wall covering has a foraminous woven fabric layer adhered to a fabric backing by a discontinuous thermoplastic polymer layer. The woven fabric preferably has an embossed undulate outer surface to enhance the acoustic properties of the lamina and to impart an aesthetic textural appearance. The individual yarns of the woven fabric are preferably substantially uniformly coated with a polyvinyl chloride plastisol to impart stain and wear-resistance, inhibit the growth of molds, fungi, bacteria and the like, and to enhance the appearance of the exposed face of the lamina. The moisture-permeable lamina structure allows wall covering paste, used to adhere the lamina to a wall, to dry at an acceptable rate, yet does not allow paste to bleed through the foraminous woven fabric layer.

FIELD OF THE INVENTION

The present invention relates to a sound-absorbing lamina and moreparticularly to a permeable, three-ply lamina usable as an acoustic wallcovering which can be secured to a wall using conventional wall coveringpaste.

BACKGROUND OF THE INVENTION

Woven fabrics having a plurality of miniature holes or openingsgenerally defined by the spaces between the interlaced threads or yarnshave been used as acoustical material on partitions, wall boards, andthe like, as between work stations in an office area. The acousticalmaterial made from a woven fabric having a plurality of miniature holesor openings have been generally laminated to an acoustical backing orsubstrate (typically fiberglass webbing or plastic foam) which is thenfastened near the edges of the wall board or partition using clips,nails, tacks, or the like.

The plurality of holes or openings in the face fabric absorb sound andare therefore essential to the acoustical characteristics of the fabric.However, the holes prevent conventional acoustical materials comprisedof woven fabric from being used as an ordinary wall covering.Conventional use of the known woven acoustical fabrics with typical wallcovering paste is impractical because the paste would flow through theopenings, thereby at least partially filling the holes and reducing theability of the fabric to absorb sound, as well as defacing the exposeddecorative surface of the fabric.

Attempts to avoid this problem and provide an acoustical wall coveringcomprising a woven fabric having a plurality of sound-absorbing holesand which can be pasted to a wall using conventional wall covering pastehave been generally unsuccessful.

One way to solve the problem is to form a lamina or plied structurecomprising an impermeable thermoplastic backing secured to an acousticwoven fabric. While the impermeable backing will prevent the paste fromflowing through and filling the holes in the woven fabric, it alsoprevents air and moisture from passing through the lamina or pliedstructure, which severely retards the rate at which the paste will dryand, consequently, promotes or at least facilitates the growth of fungusand molds, whereby unpleasant odors may be generated.

SUMMARY OF THE INVENTION

The invention generally pertains to a three-ply acoustic lamina whichcan be used as for machine application to substrates or as a wallcovering in homes, offices, and the like.

The acoustic lamina of the invention comprises a foraminous woven fabricadhered to a fabric backing by a thermoplastic polymer binder generallyin the form of a layer and generally interposed between the woven andfabric backing layers.

The thermoplastic polymer binder is a discontinuous, indiscrete layerwhich is generally, but not completely nor uniformly, situated betweenthe two fabric layers. The discontinuities such as apertures, spaces,openings, etc., in the thermoplastic polymer binder are formed duringthe laminating step of the fabrication of the acoustic lamina. Thediscontinuities in the thermoplastic polymer binder are generally smallenough to prevent the paste from flowing through when the acousticlamina is pasted to a wall, yet large enough to allow air and moistureto pass freely through, thereby maintaining the acousticalcharacteristics.

Because the fabric backing has a relatively open and porous orreticulated structure which allows for the free passage of air andmoisture, and because the woven fabric has an array of holes, apertures,openings, etc., defined by the interlaced threads or yarns, the rate atwhich moisture can escape from wet paste interposed between a wall and asheet of the acoustic lamina of the present invention is generallycontrolled by the rate at which moisture can pass through or permeatethe thermoplastic binder. Permeation rates for the acoustic lamina ofthe invention have been found to be satisfactory and, surprisingly,generally better than permeation rates for many commonly used wallcovering materials which do not possess significant sound absorbingproperties.

Fabrication of the lamina generally involves a simultaneous embossingand laminating operation wherein the three layers are brought togetherand laminated and embossed at elevated temperatures and pressures. Theexposed surface of the woven fabric layer is preferably embossed to givethe exposed decorative surface of the lamina an aesthetically pleasingtextural appearance. The embossed surface also provides undulationswhich help to absorb sound and thereby enhance the acoustical materialproperties of the lamina.

To impart stain and wear-resistance properties, inhibit the growth ofmolds, fungi, bacteria and the like, and to enhance the appearance ofthe exposed or decorative face of the lamina, a thermoplastic polymercomposition, i.e., binder, is preferably applied to the back of thewoven fabric to substantially uniformly coat the individual yarns orthreads thereof.

The three-ply acoustic lamina of the invention can be affixed to a wallor other substrate using ordinary wall covering paste, without the pasteflowing or bleeding through the lamina to the outer or exposeddecorative face of the lamina, but with air and moisture being capableof freely passing through to permit drying of the paste.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-section of an acoustic lamina in accordancewith the invention; and

FIG. 2 is a view of the woven fabric layer of the lamina along a lineperpendicular to the major dimensions of the fabric sheet.

DETAILED DESCRIPTION OF THE INVENTION

The moisture-permeable, acoustic laminas of the invention are formed bylaminating a foraminous woven fabric layer to a fabric backing layerwith a thermoplastic polymeric binder such as a layer or film interposedtherebetween. During the laminating process the three layers are exposedto elevated temperatures and pressures which cause the material of thethermoplastic polymeric film layer to melt and flow into and aroundopenings or pores in the fabric layers and thereby adhere or bind thefabrics together when the thermoplastic material re-solidifies. Alsoduring the lamination process, as the material of the thermoplastic filmflows into the fabric layers, the thermoplastic binder becomesdiscontinuous so that air and moisture will pass through and easilypermeate the lamina.

A schematic cross-section of a moisture-permeable, acoustic lamina 10 inaccordance with the principles of the invention is shown in FIG. 1. Thelamina 10 has a woven fabric layer 12 of generally any weave, with onespecific weave being shown in FIG. 2 comprising two sets of parallelyarns or threads 14 which are interlaced with one another at rightangles. The woven fabric has a relatively open weave which leavesapertures, spaces, or openings 16 in the fabric which act to absorb orbreak-up sound waves. The woven fabric contains from about 40 to about90 percent, and desirably from about 50 percent to about 60 percent openspace. That is, the total area of the openings 16 comprises from about40 to about 90 percent of the total surface area of the fabric layer.The threads 14 can generally be made of any known natural or syntheticfiber including cotton, wool, rayon, nylon, polyester, acrylic,polyolefin fibers and mixtures thereof. The woven fabric is preferablymade of polyester and has a fiber count of from about 20 to 25 by about20 to 30 strands per inch (about 8 to 10 by about 8 to 12 strands percentimeter).

The individual yarns 14 of the woven fabric are preferably substantiallyuniformly coated with a thermoplastic polymer composition to provide astain and wear-resistant coating 18 which also enhances the appearanceof the exposed face of the lamina and inhibits the formation and growthof molds, fungi, bacteria and the like. The polymeric coating ispreferably a polyvinyl chloride plastisol comprising small, polyvinylchloride resin particles dispersed in a conventional plasticizer.

Polyvinyl chloride plastisols are well known to the art and to theliterature, and can be formulated to give desired characteristics byusing numerous conventional chemical components. Most important to anyplastisol formulation is the selection of plasticizers. Examples ofsuitable plasticizers which can be used include butyl octyl phthalate,dioctyl phthalate, hexyl decyl phthalate, dihexyl phthalate, diisooctylphthalate, dicapryl phthalate, di-n-hexyl azelate, diisononyl phthalate,dioctyl adipate, tricresyl phosphate, cresyl diphenyl phosphate,polymeric plasticizers such as adipic acid polyester, azelaic acidpolyester and sebacic acid polyester, epoxidized soybean oil, octylepoxy tallate, isooctyl epoxy tallate and mixtures thereof. The amountof plasticizer used may vary from about 30 to 100 parts by weight per100 parts by weight of resin, with from about 50 to about 75 parts byweight being preferred. Examples of the other conventional componentswhich can be incorporated into the polyvinyl chloride plastisolcomposition, include various silicas such as precipitated silica, fumedcolloidal silica, calcium silicate and the like, ultraviolet lightabsorbers, fungicides, barium-cadmium-zinc stabilizers, barium-cadmiumstabilizers, tin stabilizers, dibasic lead phosphite, antimony oxide,and pigments such as titanium oxide, red iron oxide, phthalocyanine blueor green, and the like. The pigments and other additives or compoundingingredients are used in effective amounts to control color, mildew,stabilization, etc. of the plastisol.

The coating is applied to the woven fabric in an undersaturated amountsuch that all of the threads 14 are substantially coated, but so that asignificant number of the openings 16 defined by the interlaced threads14 are not blocked. The amount of the surface area of thediscontinuations, openings, spaces, etc., based upon the total surfacearea of the woven fabric layer after deposition of the plastisol isgenerally from about 35 percent to about 65 percent and preferably fromabout 40 percent to about 45 percent open.

The exposed face of the polymer-coated woven fabric, that is, the outersurface of the woven fabric which is viewable after the lamina isadhered to a wall or other substrate surface, is preferably printed witha suitable polymer-receptive ink to form desirable decorative patternsand designs. Such inks are well known and can be applied by variousmethods of printing such as by gravure, flexography, screen printing,jet printing, web printing, etc. The printing operation may be repeatedmany times, as needed, to vary the colors and designs. The printing canbe performed either before or after the woven fabric, polymeric binderand nonwoven fabric have been laminated together.

The polymer-coated woven fabric, whether printed or not printed, ispreferably embossed to provide an aesthetically pleasing undulatetexture which also enhances the ability of the lamina to absorb orbreak-up sound waves and serve as an acoustical material. The embossingoperation can be performed on the coated woven fabric before laminationof the layers, on the exposed face of the completed lamina, orsubstantially simultaneously with the laminating operation.

The amount of the various components of the woven fabric can generallyvary over a wide range with the weight of the uncoated woven fabricbeing preferably in the range between 2 and 4 ounces per square yard (68to 136 grams per square meter). The amount of coating applied to thewoven fabric is generally in the range between 4 and 6 ounces per squareyard (136 to 203 grams per square meter) of fabric, and the total weightof the coated woven fabric used in the invention is preferably from 6 toabout 10 ounces per square yard (203 to 340 grams per square meter). Thetotal average thickness of the woven fabric is generally from about 0.01to about 0.05 inches (from about 2.54 millimeters to about 12.7millimeters).

A particularly suitable plastisol-coated woven fabric which can be usedin the invention is available from GenCorp Polymer Products, Maumee,Ohio, and sold under the trademark "WebCore." The "WebCore" fabric has atotal weight of about 8.0 ounces per square yard (272 grams per squaremeter), a vinyl plastisol weight of about 5.0 ounces per square yard(170 grams per square meter), and a fabric weight of about 3.0 ouncesper square yard (102 grams per square meter). The "WebCore" fabric ismade of polyester, has a thread count of 22×26 strands per inch, and atotal average fabric thickness of about 0.018 inches (4.57 millimeters).

The fabric backing layer 40 is made from a porous or reticulate fibrousmass having a high void volume and through which air and moisture canfreely pass. The backing layer can be any fabric which is woven,nonwoven, e.g., a mat, or the like. Suitable materials for the fabricbacking include synthetic fibers such as polyester, nylon, acrylic,natural fibers such as cellulose, cotton or wool, mineral fibers such asglass, and mixtures thereof. Blends of polyester and cellulose fibersare preferred, with the amount of cellulose fiber being from about 50 toabout 85 percent, and preferably from about 60 to about 70 percent byweight, with the balance being polyester fiber. An example of a specificone-ounce fabric backing which is suitable for use with the invention isavailable from C. H. Dexter, Windsor Locks, Conn. The thickness of thebacking layer is not critical and can generally be in the range betweenabout 5 and 12 mils (about 0.127 and 0.305 millimeters), and preferablyfrom about 6 to about 8 mils (about 0.152 to about 0.203 millimeters).

The film or layer used to bind the woven fabric to the fabric backinggenerally comprises any thermoplastic material having a meltingtemperature of from about 200° F. to about 300° F. (from about 93° C. toabout 149° C.), desirably from about 230° F. to about 260° F. (fromabout (110° C. to about 127° C.), and preferably from about 250° F. toabout 275° F. (from about 121° C. to about 135° C.). Particularlysuitable thermoplastic films which can be utilized include variouspolyesters, polypropylenes and polyethylenes, with polyethylene beingpreferred. The thickness of the thermoplastic film layer prior tolamination should generally be from about 2 to about 5 mils (from about0.05 to about 0.13 millimeters), and preferably from about 2 to about2.5 mils (from about 0.05 to about 0.065 millimeters).

Fabrication of the acoustic lamina of the invention generally involves asimultaneous embossing and laminating operation. The three layers areoverlayed or superimposed with the thermoplastic film binder between thewoven fabric and fabric backing layer, and then laminated (andpreferably embossed) at elevated temperatures and pressures. Thetemperatures are from about 250° F. to about 325° F. (from about 121° C.to about 163° C.) and preferably from about 260° F. to about 300° F.(from about 127° C. to about 149° C.), with suitable pressures beingfrom about 800 to about 1500 psi (from about 56 to about 105 kilogramsper square centimeter) and preferably from about 900 to about 1,100 psi(from about 63 to about 77 kilograms per square centimeter). Methods andapparatus for laminating sheet materials at elevated temperatures andpressures are well known to the art and to the literature and generallycomprise the steps of unrolling and bringing together the individualsheets in overlaying or superimposed relation and passing the juxtaposedsheets through a pair of laminating rollers which heat and exert highpressures on the sheet material, causing the thermoplastic binder tomelt and flow into the fabric layers to bind them together upon coolingand re-solidification of the thermoplastic. During the laminatingoperation the thermoplastic film flows and becomes discontinuous leavingholes, openings, etc., through which air and moisture can permeate, asnoted above.

A schematic of the acoustic lamina of the present invention is shown byFIG. 1. The acoustical lamina, generally indicated by the numeral 10,contains a woven fabric layer 12, as described hereinabove with onespecific example being as shown in FIG. 2. Woven fabric layer 12 isbound to fabric backing layer 40 through thermoplastic binder 30 in amanner as described hereinabove. Inasmuch as binder layer 30 flows intoboth the woven and nonwoven fabric layers, discontinuities, openings,apertures, etc., exist such that, as noted above, paste from the backside of layer 40 generally cannot penetrate the binder layer and yet aircan penetrate the acoustical layer, the binder layer, as well as thenonwoven fabric layer.

The acoustic lamina of the invention can be used as an acoustic coveringfor a variety of substrate surfaces, but is particularly useful as anacoustic wall covering which can be affixed to a wall with commonly usedand/or conventional wall covering pastes. Generally, the acoustic laminais pasted to a wall in a conventional manner by spreading paste over thefabric backing of the lamina and contacting the pasted side of thelamina with the wall surface to adhere the lamina to the wall.

One of the important features of the invention is that it provides anacoustic wall covering to be pasted to a wall or other substrate surfacewithout the paste bleeding through the openings of the foraminousfabric, coating, etc., while at the same time permitting moisture fromthe paste to permeate through the lamina to allow the paste to dry. Thevoid or openings of the entire laminate is generally less than 30percent, desirably less than 20 percent, and preferably less than 15 or10 percent.

Permeability tests were conducted to demonstrate that the lamina of theinvention has a higher permeability than various conventional wallcoverings. The results for samples tested at 70° F.±1° F. (21° C.±0.5°C.) and 65 percent relative humidity ±2 percent are listed in Table I.

                  TABLE I                                                         ______________________________________                                        WALLCOVERING SAMPLE   PERMEABILITY                                            ______________________________________                                        Type II 20 oz. Osnaburg.sup.1                                                                        1.60 perms                                             Type I 12 oz. scrim.sup.2                                                                            2.28 perms                                             Perforated 10 oz. scrim.sup.3 (competitor's)                                                        13.63 perms                                             FiberTeck.sup.4       27.17 perms                                             Acoustic lamina.sup.5 of the invention                                                              72.00 perms                                             ______________________________________                                         .sup.1 Type II  20 oz. Osnaburg                                               1.8 oz/yd.sup.2 (61.2 grams/meter.sup.2) Woven Fabric Polyester/Cotton        Blend                                                                         11.7 oz/yd.sup.2 (397.8 grams/meter.sup.2) PVC Vinyl Compound Coating         .021 inches (5.33 millimeters) gauge                                          .sup.2 Type I  12 oz. Scrim                                                   1.0 to 1.1 oz/yd.sup.2 (254 to 280 grams/meter.sup.2) Woven Fabric            Polyester/Cotton Blend                                                        6.7 oz/yd.sup.2 PVC Vinyl Compound Coating                                    .017 inches (4.32 millimeters) gauge                                          .sup.3 Perforated 10 oz. Scrim (Competitor's)                                 1.1 oz/yd.sup.2 (280 grams/meter.sup.2) Woven Fabric Polyester/Cotton         Blend                                                                         11.6 oz/yd.sup.2 (394.4 grams/meter.sup.2) PVC Vinyl Compound Coating         .018 inches (4.57 millimeters) gauge                                          (Reported to have 40,000 micro holes per linear yard.)                        .sup.4 FiberTeck                                                              11.7 oz/yd.sup.2 (397.8 grams/meter.sup.2) Polyolefin Woven Fabric Acryli     coating on back                                                               .035 to .038 inches (7.87 to 8.55 millimeters) gauge                          .sup.5 WebCore Plus  Glenshire Pattern 8.4 oz/yd.sup.2 (286                   grams/meter.sup.2                                                             3.0 to 3.2 oz/yd.sup.2 (103 to 109 grams/meter.sup.2) Polyester Woven         Fabric                                                                        4.0 oz/yd.sup.2 (136 grams/meter.sup.2) PVC Plastisol Coating                 .4 oz/yd.sup.2 (13.6 grams/meter.sup.2) Binder Layer                          .75 oz/yd.sup.2 (25.5 grams/meter.sup.2) Secondary Backing                    .024 inches (6.1 millimeters) gauge                                      

The results are expressed in units of "perms" which is a term used inthe industry corresponding to grams of moisture (water) permeating thesample per square meter per hour under specified conditions. The resultsshow that the acoustic lamina of the invention has a permeability ofmore than twice that of the most permeable conventional wallcoveringtested, and that the paste used to adhere the lamina of the inventioncan be expected to dry rapidly. Generally, the acoustic lamina of thepresent invention has a permeability of from about 40 to about 500 anddesirably from bout 55 to about 200 perms.

While in accordance with the Patent Statutes, the best mode andpreferred embodiment has been set forth, the scope of the invention isnot limited thereto, but rather by the scope of the attached claims.

What is claimed is:
 1. A moisture-permeable acoustic lamina comprising;a woven fabric adhered to a fabric backing by a discontinuousthermoplastic polymer layer.
 2. The acoustic lamina of claim 1, whereinthe woven fabric has an embossed undulate outer surface.
 3. The acousticlamina of claim 1, wherein the individual yarns of the woven fabric aresubstantially coated with a thermoplastic polymer composition.
 4. Theacoustic lamina of claim 3, wherein the thermoplastic polymer coatingcomposition is a polyvinyl chloride plastisol.
 5. The acoustic lamina ofclaim 4, wherein the coated woven fabric is at least 35 percent to about65 percent open.
 6. The acoustic lamina of claim 5, wherein the wovenfabric is of polyester and wherein the thread count is from about 8 to10 by about 8 to 12 strands per centimeter.
 7. The acoustic lamina ofclaim 4, wherein the weight of the polyvinyl chloride plastisol is fromabout 136 to about 203 grams per square meter of fabric, the weight ofthe woven fabric is from about 68 to about 136 grams per square meter,and the total weight of the polymer coated woven fabric is from about203 to about 340 grams per square meter.
 8. The acoustic lamina of claim4, wherein the fabric backing is formed of polyester, cellulosic, orglass fibers, or mixtures thereof.
 9. The acoustic lamina of claim 4,wherein the fabric backing is formed from a blend of from about 50percent to about 85 percent cellulosic fibers and from about 50 percentto about 15 percent polyester fibers.
 10. The acoustic lamina of claim9, wherein the thickness of the fabric backing is from about 0.127 toabout 0.305 millimeters.
 11. The acoustic lamina of claim 4, wherein thethermoplastic polymer layer has a melting point temperature of fromabout 93° C. to about 149° C.
 12. The acoustic lamina of claim 10,wherein the thermoplastic polymer layer is polyethylene, and has amelting point temperature of from about 230° F. to about 260° F.
 13. Theacoustic lamina of claim 12, wherein the thermoplastic polymer binder isformed from a film having a thickness of from about 0.127 to about 0.305millimeters, wherein said woven fabric has an undulate outer surface,and wherein the acoustic lamina has a moisture permeation of from about40 perms to about 500 perms.